This invention relates generally to machine booms, and, more particularly to a control for controlling the boom extension velocity and boom elevation velocity.
Many machines, including, for example, telehandlers, include booms. Generally an implement such as, for example, a bucket, fork tines or basket, is located at the end of the boom for manipulation by the operator. A typical boom can be extended over 20 feet (6.1 meters) and can be elevated up to an angle of approximately 80 degrees with respect to the machine.
In a typical machine the raising and lowering of the boom is accomplished by a hydraulic boom lift cylinder. Extension and retraction of the boom is accomplished by a hydraulic boom telescoping cylinder. An operator control lever is moved along a first axis to raise or lower the boom, and along a second axis to extend or retract the boom. The velocity of raising or lowering the boom and the velocity of extending or retracting the boom is controlled by the amount of displacement of the control lever from a reference position. One difficulty with present boom controls is that as the boom is either extended or elevated relative to the machine it becomes very difficult for the operator to precisely control movement of the end of the boom in space.
Thus, it would be desirable to provide a boom extension and boom angle control that permitted a more precise control of the end of the boom as the boom was extended and/or as the boom was elevated relative to the machine. It would be especially desirable if the increase in control were accomplished without need for the operator to manipulate controls other than the control lever.
The present invention is directed to overcome one or more of the problems as set forth above.
In one aspect of this invention, a method for controlling a boom of a machine is disclosed. This method includes the steps of detecting a boom length of a boom on a machine and generating a boom length signal, detecting a boom angle of the boom and generating a boom angle signal, selecting a desired pivot velocity for the boom and transmitting a first pivot velocity signal, detecting the boom length signal, the boom angle signal, and the first pivot velocity signal and generating a second pivot velocity signal, the second pivot velocity signal equal to the sum of a constant and the first pivot velocity signal minus the sum of the boom length signal and the boom angle signal, and pivoting the boom at a pivot velocity associated with the second pivot velocity signal.
In another aspect of the present invention a boom control apparatus is disclosed. The boom control apparatus includes a boom having a boom angle sensor detecting a boom angle and generating a boom angle signal and a boom length sensor detecting a boom length and generating a boom length signal, and the boom pivotable about a pivot point on a machine, a hydraulic boom lift cylinder having a first end attached to the boom and a second end attached to the machine, extension of the boom lift cylinder pivoting the boom upwardly and retraction of the boom lift cylinder pivoting the boom downwardly, a control lever, movement of the control lever from a reference position along a first axis selecting one of a plurality of desired pivot velocities and transmitting a first pivot velocity signal based on the relative displacement of the control lever from the reference position, an electrohydraulic control module, the control module detecting the boom angle signal, the boom length signal, and the first pivot velocity signal, the control module generating a second pivot velocity signal equal to the sum of a constant and the first pivot velocity signal minus the sum of the boom angle signal and the boom length signal, and an electrohydraulic valve, the valve detecting the second pivot velocity signal and adjusting a flow rate of a hydraulic fluid into or out of the boom lift cylinder, the flow rate into or out of the boom lift cylinder pivoting the boom at a pivot velocity associated with the second pivot velocity signal.